2-mercaptooxazolines as developer retarders



Z-MERCAPTOOXAZOLINES AS DEVELOPER RETARDERS Ernest T. Larson, Jr.,Binghamton, and Harold A. Levine, Vestal, N. Y., assignors to GeneralAniline & Film Corporation, New York, N. Y., a corporation of DelawareNo Drawing. Application November 9, 1956 Serial No. 621,213

9 Claims. (Cl. 9666) This invention relates to the use of2-mercaptooxazolines as developer retarders for improved sensitometriccharacteristics in photographic films and papers.

The use of developer retarders and inhibitors has been known for manyyears. Thus the employment of such compounds as 6-nitrobenzimida'zole inan effort to slow down development, permit prolonged development withoutexcessive fog, increase contrast, and minimize reciprocity law failure(R. L. F.) of sensitive photographic products is well known. Similarly,S-mercapto-l-phenyltetrazole has been proposed as a developer retarderspecifically for controlling development fog.

Unfortunately these and other compounds used as developer retarders donot operate to yield optimum results for the intended purpose. Forexample, the 6-nitrobenzimidazole must be used in relatively highconcentrations and leaves much to be desired in minimizing R. L. F. Onthe other hand,-the aforesaid tetrazole causes marked loss in speed andcontrast.

It is the purpose and object of the present invention to provideimproved development retarders which.

(1) Effectively control fog without loss of speed;

(2) Minimize low intensity R. L. F.;'

(3) Achieve a high net maximum density on prolonged development withoutappreciably affecting the speed or contrast while reducing to a lowlevel the tendency toward high fog resulting from prolonged development;

(4) Make it possible to obtain normal useful negative images fromstrongly overexposed photographic materials by processing said materialsin a developer containing a relatively low concentration of thedeveloper retarder.

It has been discovered that these characteristics are portrayed by thatgroup of compounds which may be characterized as 2-mercaptooxazolinesdepicted by the following formula:

wherein R, R R and R are hydrogen, an aliphatic ethyl, etc.,alkylsulfonic acid, i. e., ethylsulfonic acid, propylsulfonic acid,etc., a cycloaliphatic radical, i. e., bornyl, camphonyl, iononyl, etc.,an aromatic radical, i. e., phenyl, chlorophenyl, nitrophenyl, tolyl,hydroxyphenyl, napthyl, hydroxynapthyl, etc., heterocyclic, i. e.,pyridyl, quinolyl, benzothiazolyl, benzimidazolyl, thiazolyl, triazolyl,pyrimidyl, pyridyl, benzoxazolyl, oxazolyl, imidazolyL'thio- In theabove general formula R, R R

The method of preparation employed in the synthesis of theZ-mercaptooxazolines of this invention follows the 2,855,301 PatentedOct. 7, 1958 "ice 2 procedures of Sergeev and Ivanovna, J. Gen. Chem, U.S. S. R. 7, 1495 (1937). This procedure comprises treating anaminoalcohol of the following general formula:

wherein R, R R and R have the values given above with carbon disulfidein alkaline solution to form a dithiocarbamic which is then esterifiedwith ethyl chloroformate. The resulting unstable dithiocarbamic ester isheated to form the Z-mercaptooxazolines.

The following equations illustrate the above series of chemicalreactions:

Heat

l SH

The Z-mercaptooxazolines contemplated for use herein are not onlyrecommended by their possession of the aforesaid characteristics, but inaddition by virtue of the fact that they are relatively inexpensive andcan be used in minimum amounts as compared to other developer retarders.

The Z-mercaptooxazolines may be employed effectively either in thephotographic developer or in a pre-bath used subsequent to exposure butprior to development. It is apparent that where the developer retarderis used in a pre-bath, its effect is manifested in the developing step.The quantity of the compound employed will be dictated by the specificend desired as subsequently indicated but in general will range from0.79 mg. to mgs. per liter of developer.

While we are unaware of the precise mechanism regarding the action ofthese substances, we have found that the results obtained are a functionof the concentration of the compound used, the particular compoundemployed, and the developer to which it is added. In high concentrationswithin the above range, the Z-mercaptooxazoline suppresses bothreciprocity law failure and fog on prolonged development. At lowerconcentrations, development is slowed down but eventual maximum speed isnot particularly impaired. At still lower concentrations, thedevelopment process is only slightly retarded while the rate of fogincrease with development is preferentially retarded. This results in afavorable differential inhibition of fog versus useful photographicdensity.

. The following examples will serve to illustrate the invention but itis to be understood that the invention is not. limited thereto.

3 EXAMPLE 1 Z-mercaptooxazoline was tested for its developer retarderand fog inhibitor properties by adding it in various concentrations to ahigh-alkali hydroquinonemetol developer and developing in this solutiona sensitometrically-exposed high speed negative film which ischaracterized by its high contrast and high maximum density coupled witha marked tendency to fog on prolonged development. Development in eachcase was carried out in a tank at 68 F. under conditions of mod erateagitation. The film was processed in the usual fashion through shortstop and fixer, and then washed. The Sensitometric characteristics weredetermined from density reading taken on an Ansco-Macbeth densitometer.The gradient values were taken at maximum gradient of theSEIISltOIIlCtI'lC' curve. The speed values were taken at net densitiesabove fog, and are expressed in arbitrary units. The net maximum densityvalues are derived from total maximum density which has been correctedfor both fog density and base density.

The characteristics of the film when developed as above for variouslengths of time up to 16 minutes without any retarder, are given inTable I.

The characteristics of the film when developed in the above developer,to which have been added Z-mercaptooxazoline in concentrations between0.79 mg. per liter and 100 mgs. per liter are given in Table II.

The characteristics of the film, when developed in the same developer,to which have been added 6-nitrobenzimidazole, a known developerinhibitor and antifoggant, in concentrations between 7.9 mgs. per literand 1000 mgs. per liter are given in Table III.

It will be seen that'the use of Z-mercaptooxazoline at a concentrationof 100 mgs. per liter enables one to develop the film to a given speedand contrast within a short time, 4 minutes, and to maintain thesecharacteristics virtually constant'during an additional 12 minuteswithout appreciable increase in development fog. This property is aunique advantage since it permits a wider tolerance of processing time.

The above 2-mercaptooxazoline was prepared as follows:

A solution of 10 gms. of ethanolamine, 11 gms. of potassium hydroxide in100 cc. of water was treated dropwise with a solution of 13 gms. ofcarbon disulfide in 80 cc. of dioxane during a period of minutes. To theorange colored homogeneous mixture which resulted, 17.8 gms. of ethylchlorocarbonate were slowly added. The reaction mixture was heated on asteambath for 30 minutes. It was then evaporated to dryness by vacuumdistillation on a hot water bath. The residue was extracted severaltimes with boiling benzene. Concentration of the benzene extract gave3.5 gms. of slightly impure Z-mercaptooxazoline which was recrystallizedto give colorless needles, M. P. 94.596.5 C. This substance is quitesoluble in water and is not precipitated on the addition of acids orbases.

EXAMPLE II High speed negative film was exposed in a time scalesensitometer and then developed in a hydroquinone-metol metaboratedeveloper for times ranging from 3 to 30 minutes. Similar films weredeveloped in the same type developer containing Z-mercaptooxazoline inconcentrations of 20 mgs. per liter and 60 mgs. per liter. Sensitometriccharacteristics observed are given in Table IV.

The fog retarding and development inhibiting activity ofZ-mercaptooxazoline are self evident.

EXAMPLE III 'Table V shows the developer retarder and development foginhibitor properties of 5-methyl-2-mercaptooxazoline. This table showsthe sensitometr'ic characteristics of the film used when developed as inExample I in the developer which contains 5-methyl-2-mercaptooxazolinein concentrations between 0.79 mg. per liter and 100 mgs. per liter.

The 5-methyl-Z-mercaptooxazoline used in this example was prepared asfollows:

A solution of 38 gms. of carbon disulfide and 11.2 gms.

of sodium hydroxide in 200 cc. of water was cooled to 10 C. and 18.8gms. of l-amino-Z-propanol was added with stirring. The mixture washeated on a steambath for two hours, cooled to room temperature and 27.1gms.

, of ethyl chloroformate were added. The reaction mixture was thenheated for thirty minutes on a steambath while the evolved carbonoxysulfide was vented. The cooled solution was neutralized, evaporatedto one-third volume, and let stand in a refrigerator. The whitecrystalline precipitate so obtained, was recrystallized from Water togive 12.3 gms. of 5-methyl-2-mercaptooxazoline, M. P. 7273 C.

EXAMPLE IV High speed negative film was developed in a developer as inExample II, which contained S-methyI-Z-mercaptooxazoline inconcentrations from 3 mgs. per liter to 60 mgs. per liter. Sensitometriccharacteristics observed are given in Table VI.

The fog retarding and development inhibiting activity of5-methyl-2-mercaptooxazoline are clearly evident.

EXAMPLE v The sensitometric characteristics of anotherZ-mercaptooxazoline, namely 4-ethyl-Z-mercaptooxazoline, are given inTable VII. It was tested with the photographic materials and developerof Example I in a range of concentrations between 0.79 mg. per liter andmgs, per liter of the developer.

The 4-ethyl-2-mercaptooxazoline used in this experiment was preparedfrom Z-amino-l-butanol by the method described in Example III.

EXAMPLE v1 The compound 4-ethyl-2-mercaptooxazoline was tested as inExample II. Sensitometric characteristics observed, are given in TableVIII.

The fog retarding and development inhibiting activity of4-ethyl-2-mercaptooxazoline are clearly evident from this table.

EXAMPLE v11 Reciprocity law failure activity of Z-mercaptooxazalines Thedata for R. L. F. are given in Table IX. In this table concentration isexpressed in mgs. of compound per liter of developer. Reciprocity lawfailure is the maximum variation in speed over a range of exposure timesfrom 1 second to 40 hours. Speed and R. L. F. are measured at netdensity 0.4. The data in the table represent a simultaneous comparisonof the results obtained with the mercaptooxazolines on one hand and 6-nitrobenzimidazole on the other.

TABLE II TABLE VI Develop- Max1- Developing Relative Maximum ConceningTime, Relative Speed at: Meximum Net zggfig Time, In Speed at: n y NetFog tration In Net Net mum Density F Minutes N et D. 0.20 Above Fog(mgs./l.) Minutes D =0.2 D 1.0 Gradient Agave g 3 0.03 0 6 1. O 0. 20 01 95 11 90 1. 27 3. 3 0. 57 0. 01 2 122 34 1. 72 2. 18 19 1. 40 0. 02 4128 40 2. O2 2. 37 30 30 1. 70 U. 02 6 141 45 2. 2. 57 3 1. 7 0.34 0 10135 48 2. 40 2. 70 6 13. 5 O. 91 0 16 135 46 2. 28 2. 74 10 47 1. 47 6.01 6 270 86 3. 09 3. 24 20 103 1. 98 0. 03 10 285 95 2. 84 3. 18 3 0. 950. 04 16 275 87 2. 2. 6 74 1. 61 0. 04 6 325 100 2. 64 3. 24 10 110 1.91 0. 06 10 475 114 2. 48 3. 10 v20 151 2. 20 0. 10 16 102 1. 90 2. 5930 186 2. 28 0. 13

TABLE VII 20 Develop- Maxi- TABLE III Concening Time, Relative Speed at:Maximum N t tratlon In Net Net mum Density F e (mgsJl Minutes D =0.2 D=1.0 Gradient Above 0g Develop- Maxi- Fog Ooncening Time, Relative Speedat: Maximum tration In Net Net mum Density (mgs./l Minutes D=0.2 D=1.0Gradient Above 1 18 52 .62 0 Fog 2 32 7 1. 2e 1. 33 0 4 36 12 1. 86 1.87 0 6 41 14 1. 85 1. 87 0 1 10 46 17 2. 20 2. O6 0 2 14 48 56 16 54 182.06 2.06 0 4 53 16 2. 08 2. 22 6 2. 85 3. 08 3. 31 10 6 86 29 2. 50 2.74 10 2. 99 2. 96 3. 48 14 10 127 39 2. 42 2. 84 16 345 120 2. 84 3. 5520 16 140 45 2. 46 2. 93 6 245 3. 30 3. 26 12 1 6 195 69 3. 30 3. 24 10335 2. 90 3. 37 22 10 230 78 3. 10 3. 30 16 350 2. 98 3. 18 48 16 230 773. 10 3. 28 24 6 285 90 2. 80 3. 21 12 10 335 97 2. 62 3. 09 34 1 16 385100 2.28 2. 74 .92 35 TABLE vm Developing Relative Maximum ai fi gTlnie, In Speed at: Density Net' Fog g Minutes Net D. 0.20 Above FogTABLE IV 3 0 0 6 0. 02 0 D 1 R 1 ti M 3' O eve oping e 2 ve aximum 0Time, In Speed at: Density Net Fog 30 1. 3 o. 39 o Minutes Net D. 0.20Above Fog 3 1. 1 0.26 0 6 6. 5 0. 81 O 10 24 1. 48 0. 01 3 47 1:02 0. 0320 65 2. 00 0. 02 6 112 1. 68 0. 05 30 69 2. 15 0. 04 10 159 1. 96 0. 093 13 0. 89 0. 02 20 182 2. 18 0. 20 6 53 1. 48 0. 03 30 269 2. 19 0. 2910 79 1. 76 0. 05 3 0. 10 O 20 112 2. 10 0. 05 6 2. 1 0. 38 0 30 129 2.19 0. 06 10 7. 6 0. 76 0 20 22 1. 31 0. 01 30 3g 3 02 3 6 4O 1. 24 0. 02TABLE IX 10 11 1'82 111 20 Ooncen- Relative 30 103 18 55 Compoundtration Gross R. L. F., Maxi- (mgsJL) Fog Percent mum Speed None 46 350100 fi-nitrobenzimidazole 1100 08 170 28 5-methyl-2-mercaptooxazoline 9016 85 38 TABLE v 60 4-ethyl-2-mercaptooxazoline 70 1s 8s 3sZ-mercaptooxazoline 130 18 100 36 Develop- Maxi- Coneening Time,Relative Speed at: Maximum Net tration In Net Net mum Density Fog We61311112 (IRES-l1) Minutes D Gradient ggg 1. A photographlc developerfor silver-halide compris- 65 mg a silver-halide developer and as adeveloper retarder 1 31 52 70 0 a Z-mercaptooxazolme of the followinggeneral formula: 2 49 16 1. 14 1. 41 0 4 49 14 1. 64 1. 77 0 R1 R1 6 5717 2. 04 1. 97 0 10 58 20 2.00 1. 96 0 RC-GRa 16 64 24 2. 12 2. 16 o 7 6265 84 2. 95 3. 27 11 N 10 350 103 3.00 3. 37 18 16 620 136 2. 50 3. 1746 (J 6 255 86 3. 04 3. 14 12 10 310 106 2. 86 3. 17 27 SH 16 610 2. 442. 80 84 75 wherein R, R R and R are selected from the class 7consisting of hydrogen, aliphatic, aromatic and heterocyclic radicals.

2. An alkaline photographic developer for silver-halide comprising asilver-halide developer and a Z-mercaptooxazoline of the followingformula:

3. An alkaline photographic developer for silver-halide.

comprising a silver-halide developer and a Z-mercaptooxazoline of thefollowing formula:

I SH

4. An alkaline photographic developer for silver-halide comprising asilver-halide developer and a Z-mercaptooxazoline of the followingformula:

I SH

5. In the development of an exposed silver-halide emulsion theimprovement which comprises efiecting such development in an alkalinedeveloper containing a developing agent for said silver-halide emulsionand in the presence of a 2-mercaptooxazoline developer retardercorresponding to the following general formula:

wherein R, R R and R are selected from the class consisting of hydrogen,aliphatic, aromatic, and heterocyclic radicals.

6. In the development of a photographic negative the step comprising thedevelopment of an exposed silverhalide emulsion in an alkaline developercontaining a developing agent for said emulsion and as a developerretarder a Z-mercaptooxazoline corresponding to the following formula:

HzC-CH2 7. In the development of a photographic negative the stepcomprising the development of an exposed silverhalide emulsion in analkalinedeveloper containing a developing agent for said emulsion and asa developer retarder a 2-mercaptooxazoline corresponding to thefollowing formula:

G AB

9. In the development of an exposed silver-halide emulsion the stepcomprising treating an exposed silver-halide emulsion with a pre-bathcontaining a developer retarder of the following general formula:

wherein R, R R and R are selected from the class consisting of hydrogen,aliphatic, aromatic, and heterocyclic radicals and then developing saidsilver-halide emulsion in an alkaline developer containing a developingagent for said emulsion.

References Cited in the file of this patent UNITED STATES PATENTSCarroll et a1 Oct. 21, 1952 UNITED STATES PATENT OFFICE Certificate ofCorrection Patent No. 2,855,301 October 7, 1958 Ernest T. Larson, J11,et a1.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column 2, lines 28 to 31 should appear as shown below instead of as inthe patent- 6 1 Heat R O R $H NH-C-SCOOCzHu column 6, TABLE VII, underthe heading Relative Net D=0.2, for 2.75 read 275 and for 2.80 read 980.

Signed and sealed this 13th day of January 1959.

[SEAL] Attest: KARL H. AXLINE, ROBERT C. WATSON, Attestz'ngOficer.Commissioner of Patents.

5. IN THE DEVELOPMENT OF AN EXPOSED SILVER-HALIDE EMULSION THEIMPROVEMENT WHICH COMPRISES EFFECTING SUCH DEVELOPMENT IN AN ALKALINEDEVELOPER CONTAINING A DEVELOPING AGENT FOR SAID SILVER-HALIDE EMULSIONAND IN THE PRESENCE OF A 2-MERCAPTOOXAZOLINE DEVELOPER RETARDERCORRESPONDING TO THE FOLLOWING GENERAL FORMULA: